Branches of Christianity?

What I'm wondering, is how Christianity got mixed up into so many different "branches", so to speak. I get that there was corruption in the Church in historical times. But it seems like there are too many different ways of practicing Christianity. It isn't enough to say you're a Christian. You're a Protestant, or a Baptist, or Presbyterian, or Catholic. I'm not trying to bomb the religion, but if the Bible states how to practice Christianity, shouldn't the religion be more unified? How did the King get away with bending the rules because he wanted to divorce his wife? He created his own religious group, how is that allowed? I'm just confused as to why it isn't one big group of followers, and why different groups fight with each other.